Simulated anodized aluminum coating composition



United States Patent US. Cl. 260-37 Claims ABSTRACT OF THE DISCLOSURE An inefiiciently dyed aluminum hydrate lake is formed by hydrolyzing an aluminum salt, preferably aluminum chloride, with ammonium hydroxide in an aqueous medium at a pH within the range of 5 to 12, preferably about 8, and adding a solution of a dye to the resulting hydro lyzed aluminum salt in the absence of laking aids to produce a translucent dyed aluminum hydrate lake wherein only a portion of the available hydrate sites are taken up by dye attachment. The resulting lake is separated, washed and dried and then ground to produce particles having a size within the range of 0.0001 to 0.002 inch in diameter. The lake particles are dispersed in a liquid resinous vehicle capable of hardening to a tough, abrasion-resistant, transparent film, the ratio of lake to vehicle being within the range of 1:1 to 1:20.

When this composition is applied to a bright reflective surface and the resinous vehicle hardened to form a film binding the inefficiently dyed lake particles to the surface, there is produced an article simulating an aluminum article having a colored anodized surface.

This application is a continuation-in-part of my copending application Ser. No. 435,040, filed Feb. 24, 1964 and now abandoned.

The present invention relates in one aspect to a coating composition that closely simulates the appearance of anodized aluminum when applied to a variety of surfaces, including non-aluminum substrates, such as stainless steel, other metals or non-metallic surfaces such as wood, ceramic or plasic. More particularly, the present invention relates to the production of a brushed mat finish in a desired color by means of a specially pigmented lacquer. Other aspects of the invention reside in the specially prepared pigments, their method of production and the articles coated with the inventive compositions.

The brushed mat finish afforded by colored anodized aluminum is very appealing and, therefore, it would be highly desirable to produce such an attractive finish on other substrates. It would be of advantage to be able to accurately control both the shade and tone of the final article. Such is not the case with an anodizing treatment since the intensity of the color will vary as the bath nears exhaustion. Furthermore, it is only practical to apply a single color at on etime from an anodizing bath.

Therefore, it is an object of the present invention to provide a coating composition that will closely simulate the appearance of anodized aluminum and which composition is applicable to non-aluminum substrates.

It is also an object of the invention to provide a method of preparing an article having applied to its surface the composition of the invention in simulation of anodized aluminum wherein the coating is stabilized against deterioration upon long exposure to light.

A further object of the invention is to provide a coating that simulates the effect or illusion of an anodized aluminum surface by creating a particular deep flatting effect.

Another object of this invention is the provision of colored lakes that are controlled as to transparency and as to color efliciency, and are capable of being accurately blended to match a desired color.

Yet another object of the present invention is to provide a coating composition by which the color effects, tone and transparency of anodized aluminum surfaces would be simulated.

A still further object of the invention is to achieve the soft metallic sheen appearance of anodized aluminum by chemical-mechanical means as opposed to electrolysis on a Wide variety of surfaces that include materials other than aluminum.

Yet another object is to provide means for producing an anodized aluminum resembling, uniformly colored finish on a large number of intricately shaped parts in the same batch with the absence of the critical controls and procedures required when coloring by anodizing.

These objects are accomplished according to the present invention by preparing a composition comprising translucent, inefliciently colored pigment particles of an aluminum oxide lake dispersed in a transparent or translucent, tough organic vehicle, which, suitably thinned, can be sprayed on or otherwise applied to metallic surfaces such as steel and other metals, or other bright reflective substrates including metallic coated non-metals. The successful appearance of the composition is dependent on the reflectiveness of the substrate; that is, it must be metallic or have a reasonably bright metallic luster; the organic vehicle must be transparent or at least translucent and must adhere well to both the color lake particles and the substrate, and must additionally be suitably tough and of an abrasion resistanct character. The inef-- ficiently colored lake particles that include a water-soluble dye adsorbed on or entrained within the particle must also be translucent or at least have some ability to transmit light.

Thus, it will be seen that the inefficiently dyed product of the invention differs both from an opaque aluminum oxide pigment and the usual highly transparent, welldyed lakes of extremely low hiding power.

The colored lake particles according to the present invention are relatively inefficient; i.e. include unbounded or free aluminum oxide which has hydrate sites which are not taken up by dye attachment. These inefficient lakes produce a deep fiatting or non-glossing effect, and result in a translucency or a limited measure of opacity that is important in the simulation or approximation of the ineificiently colored coating that results from the actual anodization of aluminum. Furthermore, these inefficient lakes do not have good hiding power while they also act to diffuse incident light by a combination of transmission, absorption, refraction and reflection. This inefiiciency is a salient feature of the present invention since these particular pigments dispersed in a transparent vehicle coated on a substrate having a metallic luster, allow a substantial portion of the light to penetrate to the bright substrate and be reflected through the coating, while refiecting and refracting other portions of light, all of which results in a soft metallic sheen effect very similar to the appealing appearance of anodized aluminum finishes.

The present coating may be readily applied to substrates other than steel, including aluminum and other metals, as well as synthetic plastic material. However, when a dark surface is being coated, it should preliminarily be brightened by application of a reflective preliminary coating, such as an aluminum flake paint to heighten the anodized illusion.

Usually, the purpose of applying coating compositions is to hide the substrate to be covered and it is, therefore, desirable to have high opacity in relatively thin films. This opacity limits the appearance of the film to the colors reflected from the coated surface. In recent times, coating compositions which possess a desirable depth luster have become very popular, particularly as automobile finishes. The term depth is not related to intensity in these latter coating compositions, but rather it implies the optical illusion of distance or thickness characteristic of metallic finishes. These metallic types of coating compositions have a transparent appearance and relatively loW hiding power and possess the following characteristics:

(1) An appearance of depth or distance of the film;

(2) An ability to change color depending on the nature and direction of the illuminating source;

(3) The ability to highlight or attract attention to changes in contour;

(4) A multicolored or polychromatic effect.

The prior art metallized compositions comprise a pig ment in a very fine state of division utilized in conjunction with aluminum flakes. The flaked aluminum pigments contributed to the value or lightness of color and provided the metallic appearance. However, so much aluminum flake pigment was required that the flake pigment either caused dulling or resulted in aluminum chalking on exposure. Furthermore, the aluminum flake pigments were subject to mottling or flooding, that is a heterogeneous pigment pattern in the applied film. The only way to avoid these difficulties was to use minimum concentrations of flake aluminum in the enamel, but, unfortunately, with the sacrifice of brightness and lightness. Another suggestion was the use of the combination of aluminum flake reflective pigments with low non-chalking opaque white pigments, but, however, this invariably resulted in a sacrifice in metallic appearance. Further, any coating composition containing aluminum flake pigments despite their desirable appearance, have a well recognized tendency to water spot, which results in a permanent discoloration of the finish. This is especially the case when the water is slightly alkaline as when it includes a detergent. It is also common to find that a mixture of aluminum flakes with a colored pigment is less lightfast than the colored pigment alone.

The compositions according to the invention has all of the advantages with non of the disadvantages of the previous metallized finishes, and also have several additional very desirable features. First of all, the compositions of present invention do not require aluminum flake pigments and, therefore, all the inherent disadvantages such as mottling, chalking and poor light fastness are obviated. A unique advantage of the present composition resides in its universal applicability to reflective substrates and the ability to closely match colors by the blending of differently colored inefficiently dyed aluminum hydrate lakes. This accurate blending of different colors can take place in the vehicle prior to application to a substrate. Another feature of the present composition is that there is some change in the incident light that travels through the translucent coating composition and translucent lake particles, and when it is reflected back therethrough, there is some change in diffusion patterns and, therefore, the visual effect produced is irregular or non-uniform. This diffusivity can be promoted by utilizing a binder having a refractive index differing substantially from that of the translucent pigment particles, thus promoting more ray deflections in the reflected light with the resultant destructive interference and additive interference producing additional diffusion effects.

The vehicle that binds the pigment particles can be any thermosetting or thermoplastic polymer that is transparent or translucent and which is compatible with the lake particles and which provides a uniform dispersion of the pigment particles and which has the required adhesive qualities with respect to both the substrate and the color lake particles. The binder can be either of the air drying or baking type. Particularly suitable vehicles include epoxy, polyurethane and polysulfone resins and certain modified acrylic type resins, such as DURACRON, manufactured by the Pittsburgh Plate Glass Company, and the baking enamel ACRYLOID A-101 polymerized ester dcrivatives of acrylic and methacrylic acids, manufactured by the Rohm and Haas Company.

Epoxy resins are thermosetting materials and are easily converted to tough, infusible solids by the simple addition of a curing agent and/ or an accelerator which further promotes the reaction. Basically, the epoxy resin is obtained by reacting epichlorohydrin with a polydroxy compound such as bisphenol A in the presence of a catalyst. Each molecule which may be represented by the formula is terminated by epoxy groups which are three-membered rings containing one atom of oxygen and two atoms of carbon arranged as follows:

The symbol n designates the number of repeating units and thus indicates the relative molecular weight of the epoxy resin. Commercially available epoxy resins could range from a low molecular weight where 11:0 to a high molecular weight where n=15.

One particularly suitable epoxy resin for use in the present invention is EPON7, manufactured by the Shell Chemical Company.

Polyurethanes are defined as the reaction product of a polyol compound and an organic diisocyanate. Such coating compositions have characteristics including rapid drying, deep gloss, excellent hardness and flexibility and good general toughness, abrasion resistance and excellent chemical resistance. The polyol constituent of the urethane can be a polyester, a polyether such as polyoxypropylene or its dial or a simple diol or triol such as glycerine, trimethylolpropane, sorbitol, methylglucoside and sucrose, or higher polyols derived therefrom. The isocyanate-polyol urethanes can be preformed to a prepolymer, which can be activated by moisture to cure to the desired hard finish. Of the diisocyanates, toluene diisocyanate is preferred, though other commercially available diisocyanates such as diphenylmethane-4-4-diisocyanate may also be used.

A particularly suitable polyurethane resin is Chemglaze Z151 Clear, sold by the Hughson Chemical Company (Lord Manufacturing Company).

Polysulfone resins are those containing the recurring unit fSO R-]- wherein R is a hydrocarbon radical. One polysulfone resin suitable for use in the invention is represented by U.S. Pat. No. 3,317,490.

The colored lake particles of the present invention must be prepared in a manner such that the resultant pigment lake particles are inefliciently dyed and are compatible with the carrier vehicle. This requires considerations completely contrary to the usual practice in the well developed laking art. The workers in that art were most concerned with achieving the most efiiciently colored particles possible; that is, the deepest and most brilliant transparent pigments. Therefore, considerations of optimum dye selection were practiced with optimum solution concentration, reaction times and temperature and laking aids such as barium chloride to facilitate precipitation of the dye, and laking lubricants such as turkey red oil were utilized in the attempts to induce the dye to precisely fit as many as possible of the available hydrate sites. These efficient transparent lakes produce a mirror effect when in a clear vehicle, and are not satisfactory for providing an anodized aluminum effect. To the contrary, the present invention is not at all concerned with achieving a brilliant inert hydrate lake, but instead intends to prepare an inefiiciently color lake where laking aids and lubricants are not employed to assist in maximizing a laking reaction and wherein the prime criteria in selection of the dye is a desirable color match to an anodized aluminum sample rather than the matching of the dye chromphore groups to the number and size of available hydrate sites or the selection of dyes of highest laking reactivity.

The selection of dye for the purposes of the present invention as stated above, is primarily determined by the color match desired. If the laking reactivity of the dye is high, the combination of the dye and aluminum hydrate is conducted under conditions to assure low or minimum dye attachment to the particle so as to achieve a lake particle that is translucent, with unused hydrate sites and free aluminum oxide that impart a measure of whiteness or opacity to the lake particle. Water-soluble dyes are to be utilized and they are applied from their aqueous solutions. There are many dyes that may be used for the purposes of the present invention, including many previously utilized to color anodized aluminum. The laking process hereinafter described permits the use of these so-called anodizing dyes in the practice of the present invention, even though these dyes have not heretofore been regarded as lakeable. This aspect of this invention, i.e. the use of the identical dyes for anodization-simulation as are used in actual anodization, produces particularly advantageous results in the color-matching and general simulation of the actual anodized aluminum effect. Suitable water-soluble dyes are disclosed in Pats. Nos. 2,927,872 and 3,079,309.

The particles of alumina hydrate are cationic (thus positive electrically) and therefore the dye molecules must be negatively charged. This occurs not because of ionic charges but because of negative energy sites due to oxygen and nitrogen atoms. These are supplied in the form of amino and hydroxyl groups, at least one of which are always present as substituents on the so-called mordant dyes, making this a particularly suitable class of dyes for use in the present invention. It has been found that at least two of the groups amino and/ or hydroxyl should be present in the dye molecule, it being understood that the hydroxyl group can form part of a carboxyl group.

Mordant dyes are not, however, always water-soluble. The water-insoluble dyes may be made soluble by treatment with sulfuric acid to add one or more of the radicals SO H. The sodium salts of such dyes will ionize in water (RSO -+Na+) and in the process, they become acid dyes by virtue of the type of ion formed by the color-yielding portion R of the dye molecule.

As examples of mordant dyes suitable for use in the invention, there may be named the following: Aluminum Blue LLW (C.I. Mordant Blue 69), Aluminum Fiery Red ML (C.I. Mordant Red 84), Aluminum Red RLW (Cl. Mordant Red 83), Aluminum Red GLW (Cl. Mordant Red 82), Aluminum Golden Orange RLW (Cl. Mordant Yellow 59), Aluminum Deep Red LW manufactured by Carbic-Hoechst Corporation of Morningside, N.J., Aluminum Golden Orange 2RL also manufactured by Carbic- Hoechst Corporation, Mordant Brown 4 (CI. 11335), Mordant Green 24 (CI. 11395), Mordant Brown Dye (CI. 11830), Mordant Yellow 57 (CI. 13995), Mordant Black 15 (CI. 15690) and Mordant Blue 4 (CI. 15695).

As examples of dyes which are water-soluble because of sulfonation, there may be mentioned the following: Calcocid Alizerine Blue SAP (C.I. Acid Blue 45), Acid Violet 20 (CI. 16625), Acid Orange 72 (CI. 18740), Direct Blue 33 (CI. 31635), Direct Brown 79 (CI. 30050) and Direct Black 78 (CI. 30015).

The particle size of the final color lake is related to several important visual effects. Generally, coarser particles give fuller and richer pigments, while finer particles result in paler and duller products. To achieve the desired opacity and hiding power, the particle size of pigments is controlled to result in a particular degree of scattering of incident light. It has been demonstrated that the light scattering function increases initially to a range of maximum scattering and then as particle size increases further, a rather abrupt drop in scattering power results. Another consideration is the behavior of the particles in the coating vehicle. If the particles are too large, the resultant surface after the coating composition dries, will be grainy and bumpy while if the particles are too fine, the resultant surface will appear flat. For close simulation of a brushed mat anodized aluminum surface, it has been found that the lake particles according to the present invention should range in size from 0.0001 to 0.002 inch in diameter.

The laking procedure according to the present inven tion is actually simpler than that of the prior art since dye maximizing additives are not utilized. Moreover, the prior art preparation of the aluminum hydrate proceeded from a sodium carbonate or sodium aluminate hydrolysis of aluminum sulfate. It has been found, however, that with the use of ammonia in water or other basic com pounds capable of coordination as the hydroliyzing media, there is produced a dyed lake that does not decolorize on washing, whereas sodium salt systems decolorize when washed repeatedly in alkaline solution and, in fact, even mild water washing will cause decolorization.

By way of theoretical explanation, chemically the NH radical is the source of a good hydrogen bonding unit such as the amino (NH group. It is thus capable of acting as a bonding bridge between the negative atoms in a dye molecule and the negative oxygen atoms of an aluminum oxide substrate. Such bonding extends the distances over which a dye molecule capable of forming two bonds per molecule geometrically spans the substrate surface since the bond lengths are increased at the points where such difunctional dye molecules are adhered to the substrate atoms. Therefore, dyes which do not possess the exact configuration to fit the A1 0 substrate pattern are brought into range and are bonded. However, while this mechanism is an aid to chemical bonding and consequently provides a wider dyestuff choice, it still does not produce highly eificient, brilliant lake colors. The ammonia or other base is also believed to physically participate in the laking out procedure. The chemical reactions involved are as follows:

A1203 211120 3(NH4)2SO4 In both of these reactions, the final products are the dyed aluminum oxide substrate, an NH Cl or (NH SO ammonium salt and dyestuff. It is believed that these ammonium salts lake out the dyes in a manner similar to the BaCl or AlCl laking aids previously utilized since with the corresponding use of the sodium salts the lakes are not color-fast.

The inefficiency or non-brilliancy of the lake colors of the present invention is provided by making less sites of the lake available for dye attachment. This results in more residual aluminum oxide and hydroxide sites with their attendant effects. Thus, light reflected from the metallic substrate is diffused differently than when all sites are occupied with dye. This, moreover, gives closer simulation to an anodized finish which is substantially A1 0 and dye. Thus, such a finish can be simulated in a controlled manner.

This control is provided by controlling olation that is the polymerization of the aluminum oxide. Under certain pH conditions, the Al(OH) which is formed converts into the white (Al O Thus valence sites normally available for dye attachment are bound in the polymer chain. This effect can be induced over a pH range of from about 5 to about 12. At a pH of 8 the optimum production of the white A1 0 occurs. Higher temperatures and longer exposure times and more alkaline washes also favor the olation of the product toward white.

Furthermore, the lake preparation of the present invention utilizing aluminum chloride and aluminum hydroxide, produces an effective bond between the dye and the ammonium hydroxide precipitate, permits the removal of residual chlorine by subsequent washing which improves the resistance of the coating to attack by writing inks and permits an improved cure of certain coating vehicles, such as polyurethanes.

To color the lakes, a water-soluble dye is separately dissolved in water and this solution warmed to a temperature from 40 C. to 80 C., to 50 C. to 60 C. being optimum, and it is then filtered and the filtarte added to the above described aluminum solution and stirred well. The usual aluminum chloride or barium chloride dye fixing agents are not utilized nor is the solution necessarily boiled as usually practiced to fix as much dye as possible on or within the lake. An inefiiciently dyed aluminum hydrate results, which is filtered off and washed twice more by remixing with a quantity of water with subsequent filtering. The water-washed dyed aluminum hydrate is dried and ground in a device such as a mortar to the desired size range, and the dried powder is then finish-washed six times to remove all traces of chlorine from the dyed aluminum hydrate. A 1% solution of ammonium hydroxide is a particularly effective wash solution since it serves to improve the filtration rate. The dyed aluminum hydrate is finally dried at 300 to constant weight.

A specific example of preparing an inefiiciently colored lake according to the present invention is as follows:

EXAMPLE 1 To 125 grams of anhydrous aluminum chloride (AlCl 6H O) dissolved in 300 cc. of water is added sufficient ammonium hydroxide (NH OH) to bring the pH of the solution to 8. In a separate container, a dye solution is prepared by dissolving two grams of Calcocid Alizerine Blue SAP in 100 cc. of water by warming the solution to 5560 C., filtering the solution and collecting the filtrate. This filtrate is then added to the solution of aluminum chloride and stirred well.

The now dyed aluminum hydrate is filtered off and twice washed by remixing with 1000 cc. portions of water and subsequently filtered. The water-washed, dyed aluminum hydrate is dried and then placed in a mortar and there dryground to a rough sharp edged configuration having a size range of from 0.0001 to 0.002" in diameter. The dried, ground powder is thereupon finish-washed six times to remove all traces of chlorine from the dyed aluminum hydrate. Each wash solution comprises a 250 cc. portion of a 1% ammonium hydroxide solution in water. The dried powder is mixed with each portion in a separate container and filtered between each wash. The dyed aluminum hydrate is finally dried at 300 F. to constant weight. The lake particles prepared as above were inefificiently colored and translucent and had refractive indices of about 1.6:02.

The procedure of this example was followed exactly except that in separate experiments, there was substituted for Calcocid Alizerine Blue SAP each of the following dyes: Aluminum Blue LLW, Aluminum Deep Red LW, Aluminum Golden Orange 2RL, Mordant Brown 4, Mordant Green 24, Mordant Yellow 57, Mordant Blue 4, Acid 8 Violet 20, Direct Blue 33 and Direct Black 78. In each case, the resulting product was inefficiently colored and translucent.

Such dyed lakes are now ready to be added to transparent or translucent vehicles for application to bright reflective substrates. The substrate surface, if metal, such as steeel, may be either polished, mildly etched or mildly brushed, the important consideration being that the surface should be such as to provide a good bond with the coating vehicle and be bright and reflective. Additionally, the coating bond, abrasion resistance and ink resistance may be enhanced by the use of a thin pre-coating layer of epoxy, or of a mixture of epoxy and urethane, of a viscosity of about 16 seconds when measured with a #2 cup. About one part of the inefiicient blue color lakes described above is optimum for providing the color effect in five parts of vehicle, though this may be varied from 1 to 20 parts to 1 to 1 parts with the corersponding lighter and darker effects so obtained. A specific exmaple of a coating composition and its application to steel is described below:

EXAMPLE 2 One part of the inefficient blue color lake of Calcocid Alizerine Blue SAP on aluminum hydrate prepared according to Example 1 was dispersed as the colorant in 5 parts of a vehicle comprising a polyurethane of trimethylopropane and toluene diisocyanate in stoichiometric proportions. The coating composition was ball-milled to a uniform color and thinned with anhydrous methyl ethyl ketone (MEK). A uniformly thick coating of this composition was sprayed or otherwise applied to a stainless steel surface and after baking at 300 F. for about 15 minutes to accelerate the cure, the resulting article appeared pleasingly similar to a blue anodized aluminum surface. The baked coating was found to adhere well both to the lake particles and to the substrate and was of a tough and abrasion resistant character.

The process of this example was repeated exactly except that there was used in the separate procedures in place of Calcocid Alizerine Blue, each of the following inefficiently dyed products, the preparation of which was also described in Example 1: Aluimnum Blue LLW lake, Aluminum Deep Red LW lake, Aluminum Golden Orange 2RL lake, Mordant Brown 4 lake, Mordant Green 24 lake, Mordant Yellow 57 lake, Mordant Blue 4 lake, Acid Violet 20 lake, Direct Blue 33 lake and Direct Black 78 lake. The process of this example was also repeated with each of the lakes named, using in place of the polyurethane vehicle, the following vehicles: An epoxy resin, EPON-l007, a polysulfone resin prepared in accordance with US. Pat. No. 3,317,490 and the modified acrylic resin Duracron.

In each case, the exact chroma of anodized aluminum is matched. It is to be understood, of course, that individual lakes may be blended to produce a desired effect.

While, as stated, the above-described method results in the preparation of an article closely simulating one of aluminum having an anodized surface, it has been found that some deterioration of the applied coating compositions of the invention results upon long exposure to light containing ultraviolet radiation. This problem is solved by applying over the colored layer, a layer of clear, transparent resin containing a substance which absorbs radiations over a wide band of the ultraviolet spectrum. Little is accomplished using one of the numerous agents which absorb only a limited portion of this spectrum, and it has been found that the ultraviolet light absorber Tinuvin 327, manufactured by the Geigy Chemical Corporation, is particularly effective, this substance having a specific extinction coefficient of 10 for 390 millimicron waves in chloroform. Tinuvin-327 is a substituted hydroxy-phenyl benzotriazole and it is characterized by low volatility, good color and superior washfastness properties.

Tinuvin-327 has adequate solubility in the solvents commonly used in the application of resinous coatings, and it may be incorporated in any of the liquid resinous vehicles described above in connection with the coating compositions of the present invention. The clear composition containing the ultraviolet absorber is applied after the lakecontaining composition has been applied and set. Application is preferably by spraying, but any other conventional procedure may be employed.

After the liquid resinous composition containing the ultraviolet light absorber has been applied and set, there results an article, the appearance of which remains stable over an indefinite period of use.

I claim:

1. A method of preparing a composition for coating a bright reflective surface to simulate the effect of anodized aluminum, comprising hydrolyzing an aluminum salt with ammonium hydroxide in an aqueous medium at a pH within the range of 5 to 12; adding to the hydrolyzed aluminum salt in the absence of laking aids, an aqueous solution of a water-soluble dye having in the molecule at least two members selected from the group consisting of amino and hydroxyl to produce a translucent dyed aluminum hydrate lake wherein only a portion of the available hydrate sites are taken up by dye attachment; separating said lake from said aqueous medium; washing said separated lake to remove water-soluble impurities; drying the Washed lake; subdividing the dried lake to form particles having a size range of from 0.0001 to 0.002 inches in diameter; and dispersing said particles in a liquid resinous vehicle capable of hardening to a tough, abrasion-resistant, transparent film to bind said particles to said surface, said vehicle being a member selected from the group consisting of epoxy, polyurethane, polysulfone and acrylic resins.

2. A method as claimed in claim 1 in which said aluminum salt is aluminum chloride.

3. A method as claimed in claim 1 in which said dye is a mordant dye.

4. A method as claimed in claim 1 in which said vehicle is an epoxy resin.

5. A method as claimed in claim 1 in which said vehicle is a polyurethane resin.

6. A method as claimed in claim 1 in which the ratio of said particles to said vehicle is from 1:1 to 1:20.

7. A method as claimed in claim 1 in which the pH of said aqueous medium is about 8.

8. A composition for coating a bright reflective surface to simulate the effect of anodized aluminum, comprising particles having a size range of from 0.0001 to 0.002 inch in diameter of a translucent dyed aluminum hydrate lake having only a portion of the available hydrate sites taken up by dye attachment, said dyed lake particles being dispersed in a liquid resinous vehicle capable of hardening to a tough, abrasion-resistant transparent film to bind said particles to said surface, the resin of said vehicle being selected from the group consisting of epoxy polyurethane, polysulfone and acrylic resins.

References Cited UNITED STATES PATENTS Re. 23,757 12/1953 Pike.

1,090,353 3/1914 Thun. 1,434,619 11/ 1922 McAllister. 2,053,208 9/ 1936 Curtis. 2,187,816 1/ 1940 Hartman. 1,868,593 7/1932 Bauman.

MORRIS LIEBMAN, Primary Examiner L. T, JACOBS, Assistant Examiner US. Cl. X.R. 260-41 

